Kotlin: Don't extract a name for a '_' parameter

I can't reproduce the exact circumstances, but these sometimes get "<anonymous parameter X>" names and sometimes get "$noName_X" names. Whichever way, avoiding extracting a synthetic name seems safest; anyone finding the .class file and not reading the metadata indicating it came from a `_` will extract the binary name selected, or else QL will
invent a name.

Author: smowton

java/kotlin-extractor/src/main/kotlin/KotlinFileExtractor.kt

@@ -642,7 +642,7 @@ open class KotlinFileExtractor(
             if (extractTypeAccess) {
                 extractTypeAccessRecursive(substitutedType, location, id, -1)
             }
-            val syntheticParameterNames = (vp.parent as? IrFunction)?.let { hasSynthesizedParameterNames(it) } ?: true
+            val syntheticParameterNames = vp.origin == IrDeclarationOrigin.UNDERSCORE_PARAMETER || ((vp.parent as? IrFunction)?.let { hasSynthesizedParameterNames(it) } ?: true)
             return extractValueParameter(id, substitutedType, vp.name.asString(), location, parent, idx, useValueParameter(vp, parentSourceDeclaration), vp.isVararg, syntheticParameterNames)
         }
     }

java/ql/test/kotlin/library-tests/exprs/PrintAst.expected

@@ -3583,7 +3583,7 @@ funcExprs.kt:
 #   27|                 2: [Method] invoke
 #   27|                   3: [TypeAccess] int
 #-----|                   4: (Parameters)
-#   27|                     0: [Parameter] <anonymous parameter 0>
+#   27|                     0: [Parameter] p0
 #   27|                       0: [TypeAccess] int
 #   27|                   5: [BlockStmt] { ... }
 #   27|                     0: [ReturnStmt] return ...
@@ -3629,9 +3629,9 @@ funcExprs.kt:
 #   30|                 2: [Method] invoke
 #   30|                   3: [TypeAccess] int
 #-----|                   4: (Parameters)
-#   30|                     0: [Parameter] <anonymous parameter 0>
+#   30|                     0: [Parameter] p0
 #   30|                       0: [TypeAccess] int
-#   30|                     1: [Parameter] <anonymous parameter 1>
+#   30|                     1: [Parameter] p1
 #   30|                       0: [TypeAccess] int
 #   30|                   5: [BlockStmt] { ... }
 #   30|                     0: [ReturnStmt] return ...
@@ -3652,9 +3652,9 @@ funcExprs.kt:
 #   31|                 2: [Method] invoke
 #   31|                   3: [TypeAccess] int
 #-----|                   4: (Parameters)
-#   31|                     0: [Parameter] <anonymous parameter 0>
+#   31|                     0: [Parameter] p0
 #   31|                       0: [TypeAccess] int
-#   31|                     1: [Parameter] <anonymous parameter 1>
+#   31|                     1: [Parameter] p1
 #   31|                       0: [TypeAccess] int
 #   31|                   5: [BlockStmt] { ... }
 #   31|                     0: [ReturnStmt] return ...

java/ql/test/kotlin/library-tests/underscore-parameters/test.expected

@@ -0,0 +1 @@
+| test.kt:5:9:5:9 | p0 | p0 |

java/ql/test/kotlin/library-tests/underscore-parameters/test.kt

@@ -0,0 +1,7 @@
+class A {
+
+  var x: Int
+    get() = 1
+    set(_) { }
+
+}

java/ql/test/kotlin/library-tests/underscore-parameters/test.ql

@@ -0,0 +1,5 @@
+import java
+
+from Parameter p
+where p.getCallable().fromSource()
+select p, p.getName()